Crimp tool for strain relief connector and method of forming a strain relief connector

ABSTRACT

Crimp tool is for and a method forms a strain relief connector including an optical fiber, a cover enclosing the optical fiber. The cover has an inner surface, an outer surface, a first end and a second end, the first end having a tapered portion that extends radially outwardly. A sleeve surrounds the cover and has a first inner volume and a first interior shoulder, a portion of the outer surface of the tapered portion abuts the first interior shoulder. The sleeve and the cover are simultaneously compressed forming a compressed portion. The cover and the sleeve are deformed such that the cover substantially fills the first inner volume of the sleeve.

REFERENCE TO RELATED APPLICATION

This application is a division of U.S. patent application Ser. No.10/115,429 entitled Strain Relief Connector for Fiber Optic Cable andMethod of Making Same and filed Apr. 4, 2002 now U.S. Pat. No.6,726,373, and is a continuation-in-part of U.S. patent application Ser.No. 09/565,489, entitled Strain Relief Connector for Fiber Optic Cableand Method of Making Same and field May 5, 2000, now U.S. Pat. No.6,390,688, the subject matter of each of which is hereby incorporated byreference.

FIELD OF THE INVENTION

The present invention relates to a crimping tool for and a method forforming a non-adhesive strain relief connector for a fiber optic cable.More particularly, the present invention relates to an optical fiber andcover that are disposed with in a metal sleeve, the cover having atapered portion that positions the cover within the sleeve. The coverand sleeve are simultaneously compressed such that the coversubstantially fills the inner volume of the compressed portion of thesleeve. The combination of the lengths and the widths of the cover andsleeve results in a large frictional surface between the sleeve and thecover providing a strong, reliable connection.

BACKGROUND OF THE INVENTION

Strain relief connectors for fiber optic cables are common in theconnector industry. Conventional strain relief connectors have a sleevesurrounding a light transmitting optical fiber or a plurality of lighttransmitting optical fibers. The optical fibers are generally surroundedor covered and protected by a jacket or buffer material formed from aplastic. The sleeve and the fiber optic cable are then crimped using acrimping tool into a hexagonal or round shape.

Conventional crimping methods do not allow adequate lateral flow of thejacket material, in other words, the jacket material does notsubstantially flow in a direction perpendicular to the longitudinal axisof the crimp sleeve. A lack of lateral flow forces the buffer materialto flow along the longitudinal axis of the crimp sleeve, producinglongitudinal flow. Longitudinal flow places tension on the opticalfiber, possibly causing damage to or failure of the optical fiber, orchanging its optical characteristics.

In addition, conventional crimping methods have a crimp length that isshort relative to the diameter of the jacket material. Generally, thelength of the crimp is less than four times the buffer materialdiameter. This short length results in a small area of frictionalcontact between the inner surface of the crimp sleeve and the outersurface of the buffer material and may make failure of the connectormore likely under tensile or thermal stress.

Furthermore, when assembling and crimping conventional connectors, itcan be difficult to properly position the polymer cover within the metaltube or sleeve. Many conventional connectors allow the polymer cover tomove longitudinally relative to the sleeve. Also, since the polymercover is generally disposed within the sleeve, it can be difficult toascertain the exact location of the polymer cover relative to thesleeve.

Examples of prior art fiber optic cable crimp connectors are disclosedin the following U.S. Pat. No. 3,655,275 to Seagraves; U.S. Pat. No.4,738,504 to Jones; U.S. Pat. No. 5,140,662 to Kumar; U.S. Pat. No.5,317,664 to Grabiec et al.; U.S. Pat. No. 5,418,874 to Carlisle et al.;U.S. Pat. No. 5,455,880 to Reid et al.

Thus, a continuing need exists for strain relief fiber optic connectors.

SUMMARY

Accordingly an object of the present invention is to provide a strainrelief connector for a fiber optic cable that has a relatively largefrictional area between the inner surface of the crimp sleeve and thecover layer of the fiber optic cable for a strong reliable crimpconnector.

Another object of the present invention is to provide a strain reliefconnector for a fiber optic cable that has a crimped configuration thatallows for substantial lateral flow of the cover layer, puttingsubstantially no longitudinal pressure or strain on the optical fiber.

Still another object of the present invention is to provide a strainrelief connector for a fiber optic cable that has a crimp sleeve with alength that is long relative to the diameter of the cover layer,providing a large area of frictional engagement between the cover layerand crimp sleeve and the cover layer and optical fiber.

Yet another object of the present invention is to form a strain reliefconnector that has a cover, which can be optimally positioned within asleeve.

Still yet another object of the present invention is to provide acrimping tool and strain relief connector that provide optimal crimpingof the sleeve and cover in the connector.

The foregoing objects are basically attained by providing a strainrelief connector, comprising an optical fiber and a cover enclosing theoptical fiber. The cover has an inner surface, an outer surface, a firstend and a second end. The first end has a tapered portion extendingradially outwardly. A sleeve surrounds the cover, and has a first innervolume and a first interior shoulder. A portion of the outer surface ofthe tapered portion abuts the first interior shoulder. The sleeve andthe cover are simultaneously compressed, forming a compressed portion,the cover and the sleeve deforming such that the cover substantiallyfills the first inner volume of the sleeve.

The objects are further attained by a crimp tool for a strain reliefconnector, the strain relief connector being generally cylindrical andhaving first and second external shoulders. The crimp tool comprises afirst crimp portion and a second crimp portion. The first crimp portionhas a first generally planar surface with first and second ends. Thesecond crimp portion has a second generally planar surface with thirdand fourth ends. The first and second surfaces are generally alignedwhen crimping. The first and second shoulders of the strain reliefconnector abut the first and third ends and the second and fourth ends,respectively.

Other objects, advantages and salient features of the invention willbecome apparent from the following detailed description, which, taken inconjunction with the annexed drawings, discloses preferred embodimentsof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring to the drawings which form a part of this disclosure:

FIG. 1 is a side elevational view in section of a strain reliefconnector according to a first embodiment of the present invention.

FIG. 2 is an enlarged side elevational view of the fiber optic cableextending through the crimp sleeve illustrated in FIG. 1, a portion ofthe fiber optic cable and the crimp sleeve being compressed.

FIG. 3 is an end elevational view in section of the cable and sleevetaken along line 3—3 of FIG. 2.

FIG. 4 is a side elevational view of a die and the fiber optic cableextending through the crimp sleeve, illustrated in FIG. 2, prior tocompression by the die.

FIG. 5 is an end elevational view in section of the cable, sleeve anddie taken along line 5—5 of FIG. 4.

FIG. 6 is an enlarged end elevational view in section of the fiber opticcable disposed within the crimp sleeve of FIG. 5.

FIGS. 7 a–d are side elevational views in section of a strain reliefconnector according to a second embodiment of the present inventionhaving a fiber feed bushing inserted into the crimp sleeve.

FIG. 8 is a side elevational view in section of a strain reliefconnector according to a third embodiment of the present invention,having an alignment ferrule inserted into the connector body.

FIG. 9 is a side elevational view in section of a strain reliefconnector according to a fourth embodiment of the present inventionhaving an alignment ferrule inside a crimp sleeve to align separatefiber optic cables.

FIG. 10 is an end elevational view in section of a strain reliefconnector according to a fifth embodiment of the present inventionhaving a V-groove element to align separate fiber optic cables.

FIG. 11 is an end elevational view in section of a strain reliefconnector according to a sixth embodiment of the present inventionhaving a plurality of fiber optic cables extending through a crimpsleeve prior to compression.

FIG. 12 is an end elevational view in section of the strain reliefconnector of FIG. 11 after being compressed by a die.

FIG. 13 is an end elevational view in section of a strain reliefconnector according to a seventh embodiment of the present inventionhaving a plurality of fiber optic cables extending in separate orconnected crimp sleeves.

FIG. 14 is an end elevational view in section of a strain reliefconnector according to an eighth embodiment of the present inventionhaving a fiber optic cable with a coating material and a buffer layerextending through a crimp sleeve, before being compressed.

FIG. 15 is an end elevational view in section of the strain reliefconnector of FIG. 14 after being compressed by a die.

FIG. 16 is an end elevational view in section of the strain reliefconnector of FIG. 14, wherein less force was used to compress the crimpsleeve then used in the connector of FIG. 15.

FIG. 17 is an end elevational view in section of the strain reliefconnector of FIG. 14, but with plurality of fiber optic cables extendingthrough a crimp sleeve.

FIG. 18 is a side elevational view in section of strain relief connectoraccording to a ninth embodiment of the present invention.

FIG. 19 is an enlarged side view in section of the sleeve for the strainrelief connector of FIG. 18.

FIG. 20 is a side elevational view in section of the cover for thestrain relief connector of FIG. 18.

FIG. 21 is a side elevational view in section the strain reliefconnector of FIG. 18 with an optical cable extending therethrough.

FIGS. 22 a–22 b are side elevational views in section of device formingthe tapered end of the cover of FIG. 20 and of the tapered end formedthereby.

FIG. 23 is a side elevational view of another die configuration insection and the fiber optic cable extending through the crimp sleeve,illustrated in FIG. 18, prior to compression by the die.

FIG. 24 is an end elevational view in section of the cable, sleeve anddie of FIG. 23.

FIG. 25 is a side elevational view of the cable, sleeve and die of FIG.23, after compression by the die.

FIG. 26 is an end elevational view in section of the cable, sleeve anddie of FIG. 25.

FIG. 27 is a side elevational view in section of a strain reliefconnector according to a tenth embodiment of the present invention,having an alignment ferrule inserted into the sleeve.

FIG. 28 is a side elevational view in section of a strain reliefconnector according to an eleventh embodiment of the present invention,having splice element connector two sleeves.

FIG. 29 is a side elevational view in section of a strain reliefconnector according to a twelfth embodiment of the present invention,having a fiber alignment member, prior to compression by a die.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring initially to FIGS. 1–3, a strain relief connector 10 accordingto a first embodiment of the present invention has a securing member ormechanism 12 surrounding a deformable connector body 14. Spring 16 isinserted between the securing member 12 and the connector body 14. Theconnector body 14 surrounds a portion of an alignment ferrule 18 and iscoupled to a crimp ring 20. A deformable crimp tube or sleeve 22 isdisposed within the connector body and the deformable crimp tube 22 iscoupled to a fiber optic cable 24 having a cover 26 surrounding anoptical fiber 28.

The securing member 12 is preferably a tubular or round metal threadedor bayonet type nut known in the pertinent art, such as an FC or ST typeconnector or any other suitable connector. The securing member does notnecessarily have to be tubular, round, or metal and may be any type ofsecuring device that can be connected to the deformable connector body14 receiving deformable crimp tube 22.

Preferably, the securing member 12 has cylindrical inner and outersurfaces 30 and 32, respectively, the inner surface 30 defining athrough passageway 34. Additionally, adjacent the inner surface 30 thesecuring member has a cylindrical shoulder or stop 36 defining a hole38. Cylindrical shoulder 36 extends around the entire circumference ofinner surface 30 and defines a reduced diameter for a portion of throughpassageway 34.

Deformable connector body 14 is preferably a metal tubular body havingfirst and second ends 40 and 42, respectively. As seen in FIG. 1,adjacent first open end 40 is cylindrical outer surface 44. Outersurface 44 extends substantially the length of connector body 14.Extending substantially perpendicular to and away from surface 44 iscylindrical removable washer or stop 46. Stop 46 extends substantiallyaround the circumference of outer surface 44 and fits into groove 47.Outer surface 44 terminates at outwardly extending, rearwardly axialfacing surface 48 of extension 50. Extension 50 terminates at secondopen end 42, forming an enlarged radial portion of connector body 14.

Cylindrical inner surface 52 of connector body 14 defines throughpassageway 54 and is adjacent frustoconical surface 56. Frustoconicalsurface 56 tapers toward cylindrical surface 58, which is adjacentforwardly facing axial surface 60. Surfaces 56, 58 and 60 form acylindrical shoulder or stop 62, which forms a reduced radius for aportion of through passageway 54. Adjacent surface 60 is cylindricalsurface 64 that has substantially the same diameter as inner surface 52and terminates at second end 42.

Spring 16 is preferably a helical plastic or metal spring having firstand second ends 13 and 15, respectively. Spring 16 is not necessarilyhelical and may be any suitable shape or material that would be capableof biasing either the body 14 or the securing member 12, relative to theother.

As shown in FIG. 1, alignment ferrule 18 is preferably a ceramiccylindrical tube having outer surface 66 and through passageway 68.Alignment ferrule 18 does not necessarily have to be ceramic and may beany suitable material and shape that would allow it to be coupled to theconnector body 14 or the securing member 12. Preferably, ferrule 18 hasa first open end 70 and a second open end 72. Inner frustoconicalsurface 74 extends from first end 70, tapering inward toward the centerof ferrule 18. Cylindrical surface 76 is adjacent surface 74 and extendsto second end 72.

Crimp ring 20 is a preferably a metal cylindrical tube having throughpassageway 78 and first and second ends 80 and 82, respectively.However, ring 20 does not necessarily have to be metal and may be anysuitable material and shape that would allow it to be coupled to theconnector body 14. Cylindrical outer surface 84 extends from first openend 80 to one end of outwardly extending, rearwardly axially facingsurface 85 and cylindrical surface 86 extends from the other end ofsurface 85 to second open end 82. Cylindrical inner surface 88 extendsfrom first end 80 to frustoconical surface 90, which extends radiallyoutwardly from surface 88 to cylindrical surface 92, surface 92terminating at second end 82. Ring 20 facilitates coupling the connectorbody 14 to the sleeve 22.

As seen in FIGS. 4–6, crimp sleeve 22 is preferably a relatively longdeformable metal sleeve. The length of sleeve 22 is preferably at leastfive times the diameter of fiber optic cable 24 extending therethroughand is more preferably seven times the diameter of the cable 24. Crimpsleeve 22 has cylindrical inner and outer surfaces 94 and 96,respectively and initial inner and outer diameters, 98 and 100,respectively. The outer surface 96 is preferably a smooth substantiallyuniform surface extending from first open end 102 to second open end104. Inner surface 94 may be either smooth or roughened to increase thecoefficient of static friction thereon. As seen in FIGS. 1 and 2, afiber optic cable 24 extends through the sleeve 22.

As seen in FIG. 6, the fiber optic cable preferably includes of a glassoptical fiber 28 having a 125 micron (0.125 mm) outer diameter 106surrounded by cover 26. However, the optical fiber may be any suitablediameter and any suitable material for propagating light, such asplastic or the like. The cover 26 is preferably a polymer tube formedfrom a thermoplastic elastomer material, such as HYTREL 6356. HYTRELforms a family of copolyester elastomers. Typical reactants from whichthe elastomers are derived are terephthalic acid, polytetramethyleneglycol, and 1,4-butanediol. This type of elastomer is highly resilientwith a good resistance to flex fatigue at low and high temperatures, andis resistant to oils and chemicals. However, the cover may be anysuitable material that may be compressed while simultaneously protectingthe optical fiber it surrounds. The cover 26 has a 900 micron initialouter diameter 108, which is substantially smaller than the innerdiameter 98 of sleeve 22. Cover 26 surrounds optical fiber 28 andinitial inner diameter 110 of cover 26 is substantially larger than theouter diameter of the optical fiber 28.

As seen in FIGS. 2 and 3, sleeve 22 and cable 24 are compressed along aportion thereof. The deformed width of the crimp sleeve is substantiallygreater than the original un-crimped outside diameter. The deformedheight of the crimp sleeve is substantially less than the originalun-crimped outside diameter. As seen specifically in FIG. 3, theinternal portion of the present invention produces substantial verticalcompression of cover 26 of optical fiber cable 24, the coversubstantially filling the entire inner volume of the compressed crimpportion of sleeve. This vertical compression produces unique crosssectional geometries of the crimp sleeve 22 and cover 26, each having awidth in the horizontal plane substantially greater than the height inthe vertical plane.

Additionally, the volume of the deformed portion of the cover 26 isactually reduced from its original volume due to compression. The longlength of the deformed portion of sleeve 22 is such that it constrainsthe flow of cover material in the axial direction due to friction withthe internal surface of the crimp sleeve. Substantially all of the coverextends in a direction substantially perpendicular to the axialdirection or a longitudinal axis of the optical fiber and the length ofthe sleeve, limiting tensile stress in the optical fiber in alongitudinal direction. This constraint of axial flow, in addition tothe reduction in cover volume, produces increased local compression ofcover material surrounding the glass fiber, as seen in FIG. 3. Thelateral flow of cover 26 also limits the effect of axial coverelongation from inducing excessive tensile stress into the optical fiber28 in the longitudinal direction. The combination of reduced volume andconstrained flow of cover 26 results in an increase in the local densityof the cover 26. The increase in local density results in an increase inthe local elastic modulus of the material in contact with the opticalfiber 28, which contributes to an increase in pressure applied to thesurface of the optical fiber. This increase in applied pressure, over arelatively long length of area on the optical fiber, increases thefriction force required to move the optical fiber in the axial directionrelative to the deformed crimp sleeve. The increased friction force andsubsequent resistance to axial movement of the optical fiber contributesto improved performance in tensile cable retention.

Additionally, the crimp may form a laterally central-portion (not shown)extending upwardly and downwardly from of sleeve 22 and cover 26 and,aligned vertically with the optical fiber, which are not compressed tothe same extent as the remaining portions thereof. These centralportions help maintain the centrality of the optical fiber 28 within thecrimp sleeve 22 during the crimping process, and provide a slightlythicker region of cover 26 along both sides of the optical fiber in thevertical plane. These thicker, localized cover regions prevent the innersurface 96 of crimp sleeve 22 from contacting the glass fiber. Thisconfiguration adds an element of safety to the crimp technique describedherein. It should be noted that any contact of metal to the opticalfiber is undesirable, and could lead to fracture failure of the opticalfiber.

To crimp sleeve 22 to cable 24, cable 24 is extended or inserted throughsleeve 22. As seen in FIG. 4, sleeve 22 and cable 24 are then insertedinto a long flat crimp die 114 having upper and lower jaws 116 and 118,respectively. As seen in FIG. 5, jaws 116 and 118 have a width that issubstantially greater than the height thereof, permitting uninhibitedlateral flow of sleeve 22 and cover 26. By applying the proper amount ofpressure or designing the die 114 to be fully closed at the proper crimpheight, the configuration of the die compressed crimp portion of thesleeve and the compressed portion of the fiber optic cable shown in FIG.3 may be obtained.

Assembly

A portion of cover 26 is stripped away from the fiber optic cable 24,leaving an exposed portion 29 of optical fiber 28, as seen in FIGS. 2and 4. As described above, cable 24 is inserted into sleeve 22 andcrimped. Sleeve 22 and cable 24 are then inserted into connector body14, as seen in FIG. 1. Securing member 12, connector body 14, and spring16 are a preassembled conventional item that is known to one skilled inthe art. Optical fiber 28 enters ferrule 18 and extending therethroughand sleeve 22 abuts stop 62. The exposed portion 29 of optical fiber 28extends outward from alignment ferrule 18 after crimping to allow forcleaving and polishing flush to the end face. First end 40 of connectorbody 14 is then inserted into second open end 82 of ring 20 and coupledthereto by a conventional hex type crimp applied to surface 86. The hexcrimp also coupling connector body 14 to sleeve 22, and furtherprotecting sleeve 22 and fiber optic cable 24. However, it is possibleto leave out one or a plurality of the above mentioned parts. Forexample, it is possible to couple the securing member 12 directly to thesleeve 22 using crimping or any other suitable methods, to connect theferrule 18 directly to the sleeve 22 and/or to leave out the ring 20. Inaddition, it is possible to insert the fiber optic cable 26 directlyinto the connector body 14 and to crimp the connector body, as describedbelow.

Embodiment of FIGS. 7 a–d

As seen in FIGS. 7 a–d, metal sleeve 122 is substantially similar tosleeve 22, however, sleeve 122 may have a fiber feed bushing 120 andelastomer tube or cover 121 inserted therein. Sleeve 122 also hascylindrical extensions 126 and 128 extending substantially perpendicularand outwardly from surface 130. Extensions 126 and 128 facilitateinsertion and reception into connector body 14. In addition, sleeve 122has a surface 132 defining a large through passageway 134. Surface 132extends to frustoconical surface 136, which tapers inwardly and isadjacent cylindrical surface 138, which defines a small throughpassageway 139.

The bushing 120 has cylindrical inner and outer surfaces 154 and 156,respectively, inner surface 154 defining a through passageway 139. Outersurface 156 begins at first open end 160 extends to frustoconicalsurface 158, which terminates at second open end 162. Inner surface 154extends from first end 160 to frustoconical surface 164, which isadjacent conical surface 166 defining through passageway 168.

The elastomer tube 121 is similar to cover 26 and surrounds a portion ofan optical fiber or glass fiber 140, and has an inner and outer surface146 and 148, inner surface 146 defining a through passageway 150.However, the cover 121 is a separate protective section and the fiberoptic cable 142 has another cover or buffer portion 144 protecting themajority of the un-crimped or exposed portion of cable 142, a portion ofwhich is stripped away allowing the optical fiber 140 to extend throughpassageway 150.

The elastomer tube 121 and feed bushing 120 are secured within the crimptube by adhesive, interference fit, or staking or slight deformation ofthe crimp tube to permit a suitable interference fit. The buffer portion144 of the optical fiber cable 142 is received within the throughpassage way 139 of the feed bushing 120, frustoconical surface 158abutting frustoconical surface 136 of sleeve 122 when inserted therein.The exposed optical fiber 140 is received within the through passageway168 of feed bushing 120 and throughout elastomer tube 121. Throughpassageway 168 of the feed bushing 120 is preferably larger than theoptical fiber and slightly less than the internal diameter of elastomertube 121. The optical fiber also extends outward from elastomer tube121, to be received by the alignment ferrule of a typical connector orsplice, similar to FIG. 1. Preferably, the long flat crimp is applied,as described above, over the crimp tube portion only through whichelastomer tube 121 is received. However, the feed bushing 120 disposedwithin the crimp sleeve 122 may also be crimped.

Embodiment of FIG. 8

As seen in FIG. 8, metal connector body 214 has a plastic or metalalignment ferrule 218, inserted therein, as described above. Ferrule 218is substantially similar to ferrule 18 and the description of ferrule 18is applicable to ferrule 218. In the present embodiment, body 214 has aninner cylindrical surface 224 adjacent first open end 226 defining athrough passageway 228 therethrough. Surface 224 is adjacent axiallyfacing outwardly extending surface 230 that extends to cylindricalsurface 232, which terminates at second open end 234. Surface 232defining a through passageway 236 that is larger in diameter thanthrough passageway 228.

Ferrule 218 may be inserted though second end 234 and one end of ferrule218 abutting surface 230. In this configuration, the crimp, using a longflat crimp die similar to die 114 shown in FIGS. 4 and 5, is performeddirectly onto the connector body 214. Disposed within the connector bodyprior to crimping may be an fiber optic cable 238 either with thebuffered layer or optical fiber surrounded by a thermoplastic elastomertube 240, as described above. The elastomer tube 240 configuration mayhave a fiber feed bushing as described above, to aid the insertion ofoptical fiber 242 into the elastomer tube 240.

Embodiment of FIGS. 9 and 10

As seen in FIG. 9, the crimp method described above may be used tosplice two axially aligned separate fiber optic cables together. A metalcrimp sleeve 322 has inner and outer surfaces 324 and 326, surface 324defining a uniform through passageway 328. A metal or plastic fiberalignment ferrule 330, similar to the alignment ferrules describedabove, however, having a inner frustocontical surfaces 332 and 334 oneach open end 336 and 338, respectively, is positioned substantiallyequidistant from first and second ends 337 and 339 of sleeve 322, asshown in FIG. 9. Frustoconical surfaces 332 and 334 facilitate enteringof optical fibers or exposed optical fibers 340 and 342 into eachrespective end of ferrule 318. Optical fibers 340 and 342 extend fromrespective fiber optic cables in a manner described above. The twooptical fibers join together in physical contact or abut one anotherwithin the alignment ferrule at a point 343. The alignment ferrule mayhave optical refractive index matching gel to enhance opticaltransmission therethrough.

Disposed within each end of the deformable crimp tube 322 arethermoplastic elastomer tubes 344 and 346. The elastomer tubes aresubstantially similar to the elastomer tubes described above, andsurround exposed optical fibers 340 and 342, onto which the long flatcrimp is applied, in a similar manner as described above. The covers 352and 354 of the fiber cables are not necessarily crimped in thisembodiment. To aid the insertion of the fibers 340 and 342 through theelastomer tubes 344 and 346, fiber feed bushings 348 and 350 may be usedby securing into the ends of the deformable crimp tube 322, as describedabove. Fiber feed bushings 348 and 350 are substantially similar to thefeed bushings described above.

It is also possible to center the two optical fibers along a verticalaxis, using a V-groove 353 in a non-deformable cylindrical member 356,as shown in FIG. 10. Cylinder member 356 is disposed within sleeve 322similarly to ferrule 330, shown in FIG. 9 and functions in asubstantially similar manner as ferrule 330, optic fibers contacting oneanother along a length of groove 353. Only one optical fiber 362 isshown, as it is understood that member 356 may splice two or more fiberoptic cables together as described above. Preferably, cylindrical member356 is formed from glass, although it can also be plastic or metal, andhas an outer diameter 358 that is substantially smaller then the innerdiameter 360 of the elastomer tube 354. Applied in the vertical plane,the flat crimp dies deform the crimp tube, thereby compressing theelastomer 354 over the adjoined optical fibers, forcing them into theV-groove 352. This force on the fibers in the groove produces africtional force that resists axial movement or slippage of the fibersapart from each other. It is understood that the deformable crimp tube,elastomer, and V-groove element may be of circular or non-circularshape, or any shape permitting the use of a long flat crimp. The twoexposed glass fibers join together in physical contact within theV-groove, where refractive index matching gel may be applied to enhanceoptical transmission therethrough.

Embodiment of FIGS. 11–13

As seen in FIG. 11, sleeve 422, is initially oval in shape, in all otheraspects, material and length, of sleeve 422 is substantially similar tosleeve 22. Extending through sleeve 422 are fiber optic cables 424 and426, Cables 424 and 426 are substantially similar to cable 24, describedabove. It is understood that this configuration may apply to one, two,or more optical fibers disposed within either a single round or oval, ormultiple round 423 and 425, as shown in FIG. 13, or oval tubes, eitheradjacent to one another or with spacing between.

FIG. 12 shows the crimped condition of the duplex fiber configuration,shown in FIG. 11. The internal diameter of the elastomer tube collapsesin a manner to surround the optical fiber. The pressure of the elastomersurrounding the optical fiber is such that the retention strength of thefiber within the crimp will exceed prior art strain relief connectors.The crimping and assembly methods are substantially similar to thosedescribed above.

Embodiment of FIG. 14–17

Crimp sleeve 522 is substantially similar to sleeve 22 described above.However, as shown in FIG. 14, the fiber optic cable 524 has an opticalfiber 526 of a 125 micron (0.125 mm) diameter 528. Surrounding theoptical fiber is preferably an acrylate polymer coating 530 that has ofa 250 micron (0.250 mm) outside diameter 532. However, the coating maybe any suitable polymer. Surrounding the polymer coating 530 is a buffermaterial or layer 534 of a 900 micron (900 mm) outer diameter 536.Preferably the buffer layer is polyvinyl chloride (PVC), but may be anyother suitable material. Similar the cover 26 above, outer diameter 536of buffer layer 534 is substantially smaller than inner diameter 538 ofsleeve 522.

The crimping method is substantially similar to the above describedcrimping method and results in the deformed width substantially greaterthan the deformed height. As seen in FIG. 15, the internal portion ofthe present embodiment produces substantial vertical compression of thebuffer layer and coating of the optical fiber cable. This verticalcompression imparted by the flat crimp die profile produces unique crosssectional geometries of the crimp sleeve 522, buffer layer 534, andcoating material 530. The unique pattern of coating materialdisplacement is such that the coating material flows in a divergentpattern relative to the glass optical fiber, the coating materialsubstantially filling the entire inner volume of the compressed crimpportion of sleeve. The divergent pattern of the coating material 530 issuch that two circular-segmented lobes 540 and 542 of bilateral symmetryare formed adjacent to the optical fiber in the horizontal plane, asseen in FIG. 15. The formation of the divergent, circular-segmentedlobes 540 and 542 of coating material 530 permits the compressed bufferlayer 534 to contact the optical fiber 526 along two separated arcuateareas on opposite sides of the glass fiber. This change in materialcontact can only be accomplished by the flat crimp technique. The amountof divergence of the coating material in the horizontal direction isdependent on the rigidity of the buffer layer. Buffer materials ofrelatively high rigidity produce less horizontal divergence of thecoating material.

According to calculations, the volume within the internal deformedportion of the buffer layer and coating material is actually reduced.For example, the percent reduction in aggregate volume of the bufferlayer and coating material can be as much as 8%. The long length (asdefined herein) of the deformed portion of this preferred embodiment issuch that it constrains the flow of buffer material in the axialdirection due to friction against the internal surface of the crimpsleeve. A drilled finish on the internal diameter of the undeformedcrimp sleeve enhances this friction effect. This constraint of axialflow, in addition to the aggregate reduction in buffer layer and coatingmaterial volumes, produces increased local compression of buffer layerand coating material surrounding the glass fiber in FIG. 15. Similar tothe cover 26, described above, the combination of reduced volume andconstrained flow of buffer layer and coating material results in anincrease in the local density of the aggregate buffer layer and coatingmaterial and an increased friction force. The increased friction forceand subsequent resistance to axial movement of the optical fibercontributes to improved performance in tensile cable retention tests.

Additionally similar to that described above, a portion of the internalradius of the crimp sleeve and a portion of the buffer layer in thecrimped portion may remain slightly undeformed. These portions of theinternal radius and buffer layer helps maintain the centrality of theoptical fiber and prevent the deformed metal crimp sleeve internalsurface from contacting the glass fiber.

FIG. 16 illustrates a further embodiment of fiber optic cable 624 and asleeve 622. The cable 624 has an optical fiber 626 surrounded by acoating material 630, which is surrounded by a buffer layer 628 aftercrimping. In this embodiment, the deformed height is somewhat greaterthan as shown in FIG. 15, the displacement of the coating material 630is less severe, due to the height of the crimp die, the amount ofpressure exerted or the strength of the buffer layer. This deformationresults in the coating material remaining in contact around the entirediameter of the glass optical fiber. The sleeve 622 and the methods ofassembly and crimping are substantially similar to those above.

As seen in FIG. 17, a plurality fiber optic cables 724 and 726 extendthrough sleeve 722. The buffer layers 728 and 729 of each fiber opticcable 732 and 734 flows in a manner which completely fills the ovalshaped internal area of the crimp sleeve after crimping. The coatingmaterial 730 and 731 of each optical fiber 736 and 738 may deform into apattern similar to that shown in FIG. 16, or in FIG. 15 The materialsand method of crimping are similar to those described above.

Embodiments of FIGS. 18–29

FIGS. 18–21 illustrate another embodiment of a sleeve 822 and cover 826that can be used in the strain relief connector generally shown inFIG. 1. Preferably, sleeve 822 and cover 826 take the place of sleeve 22and cover 26, but sleeve 822 and cover 826 are not limited to thisparticular connector and can be used in other strain relief connectors,if desired.

As seen in FIGS. 18 and 19, sleeve 822, in its initial configuration, ispreferably a deformable metal sleeve, but may be any deformable materialand does not necessarily need to be metal. Sleeve 822 has a first end850, a second end 852 and a through passageway 854, extending from thefirst end to the second end. Sleeve 822 has an outer surface 856 with afirst protrusion or exterior shoulder 858 and a second protrusion orexterior shoulder 860. Each shoulder 858 and 860, preferably extendssubstantially perpendicularly or radially outwardly from the outersurface. In other words, the shoulders are cylindrical protrusions thatextend radially from the outer surface. First shoulder 858 is adjacentthe first end 850, while second shoulder 860 is adjacent the second end852.

Through passageway 854 begins at circular opening 862 in the first end850 and is initially defined by an interior substantially cylindricalsurface 864. Interior surface 864 is adjacent opening 862 and forms thelargest diameter portion 866 of through passageway 854. Adjacent surface864 is inwardly tapered surface 868. Surface 868 extends radiallyinwardly, and tapers in a direction away from first end 850 to reducethe diameter of through passageway 854 and to form a first interiorshoulder 870. Adjacent tapered surface 868 is a substantiallycylindrical interior surface 872. Inwardly tapered surface 874 isadjacent surface 872 and extends radially inwardly, further reducing thediameter of through passageway 854 and forming a second interiorshoulder 876. Adjacent surface 874 is a substantially cylindricalinterior surface 878, defining the smallest diameter portion 880 of thethrough passageway 854. Surface 878 is adjacent substantiallycylindrical opening 882 in second end 852 of the sleeve 822. Interiorshoulders 870 and 876 are preferably positioned in the general area ofthe exterior shoulders 858 and 860, respectively, for proper placementof the sleeve in a die compression device, as described in more detailbelow.

As seen in FIGS. 18 and 20, cover 826 is a polymer tube formed from athermoplastic elastomer material, such as HYTREL, as described above forcover 26. Cover 826 is preferably substantially cylindrical for most ofits length between a first end 884 and a second end 886. A throughpassageway 888 extends from the first end to the second end. Second end884 has a flared or tapered portion 890 that extends radially outwardly,forming a substantially frustoconical opening 896 in the first end thatis larger at one end than the substantially cylindrical opening 898 inthe second end. Cover 826 has an outer surface 892 and an inner surface894, the inner surface defining the through passageway 888.

As seen in FIGS. 22 a–22 b, the tapered portion of cover 826 is formedusing a substantially cylindrical high temperature probe 904. Probe 904has a frustoconical or tapered portion 906 with a radiused tip 908, anda stop surface 910. Initially the probe 904 is inserted into opening 896in the second end 884 of the cover 826. Since the cover 826 is athermoplastic material, the second end 884 expands and is stretched asthe tapered portion 806 of the probe 904 is pushed into the throughpassageway 888. When the second end 884 of the cover contacts stopsurface 910, the probe is withdrawn, and the tapered portion 890 isformed. This method of forming the tapered portion is the preferredembodiment. The tapered portion can be formed in any manner desired,such as originally molded or stretched in any other process known in theart.

The interior surface 894 at the tapered portion can be used to guideoptical fiber 900 into the through passageway 888. Through passageway888 is substantially cylindrical outside of flared portion 890 and issized and configured to allow an optical fiber 900 to extendtherethrough, as seen in FIG. 21. The interior diameter of cover 826 asdefined by surface 888 has a substantially larger transverse diameterthan the exterior diameter of optical fiber 900 (FIG. 21). The interiordiameter of sleeve 822 is, in turn, substantially larger than theexterior diameter of cover 826 (FIG. 21). Preferably, the respectivediameters of the optical fiber, the cover and the sleeve allow for spacebetween each element when initially assembled.

Although the exterior of the cover is generally smaller in diameter thanthe interior of the sleeve, as seen in FIG. 18, the interior shoulders870 and 876 taper inwardly toward end 852 as described above, allowingthe cover to be correctly and precisely fitted therein, by engagementtherewith. The outer surface 892 of the cover at the tapered portion 890abuts or contacts the first interior shoulder 870, preventing the coverfrom extending farther into the interior of the sleeve. Additionally,second end 886 of the cover 826 abuts the second interior shoulder 876,which also prevents the cover from extending too far through the throughpassageway 854. Either shoulder alone would prevent undesired lateralmovement or over insertion of the cover within the sleeve; however, theredundancy and design of the cover and sleeve ensure that the cover isproperly placed in the sleeve. As a further measure for proper fittingand retention, the outer surface 892 at the first end 884 of the cover,at the largest diameter of the tapered portion 890 forms an interferencefit with the interior surface 864 of the sleeve 822.

Furthermore, as shown in FIG. 21, when buffer layer 902 is disposedwithin the sleeve 822 and the flared portion of the cover 822, thebuffered layer can act as further strain relief. For example, when thecover and sleeve are compressed the cover will lengthen and extendtoward the buffer layer. This extension of the cover and contact withthe buffer layer will create an interference or frictional fit betweenthe cover and the buffer layer, which will assume some tension understrain.

As with the embodiments described above, this embodiment of sleeve andcover is crimped by a die compress crimp device or tool 910, shown inFIGS. 23–26. The crimp device 910 has an upper crimp portion or die 912and a lower crimp portion or die 914. The upper crimp die 910 has acrimp surface 916, which is substantially planar. The first end 913 ofthe first crimp die has a first shoulder or recessed portion 916 thereinand the second end 918 has a second shoulder or recessed portion 920therein. Since each recessed portion is substantially similar, onlyrecessed portion 916 will be discussed in detail. Recessed portion 916is semi-cylindrical (FIG. 24) and defined by a radially inwardly facingsemi-cylindrical surface 922 and a radially extending vertical surface924. Vertical surface 924 is adjacent crimp surface 916 and issubstantially perpendicular thereto. The corner of vertical surface 924and crimp surface 916 defines a first end or edge 926. Similarly, thevertical surface of recessed portion 920 defines a second end or edge928. Furthermore, at the sides of first crimp die 912 are recessedportions 930 and 932, which are for lateral alignment of the crimp dies,as discussed in more detail below. As seen in FIG. 24, recessed portions930 and 932 are formed by angled surfaces 934 and 936 and by horizontalsurfaces 938 and 940.

Lower crimp die 914 has a planar crimp surface 942, which is recessedfrom the rest of the crimp die. Additionally, die 914 has a first end941 with a first shoulder or recessed portion 944 and a second end 943with second shoulder or recessed portion 946. Each recessed portion issubstantially semi-cylindrical. Since each recessed portion issubstantially similar, only portion 944 will be described in detail. Asshown in FIG. 23, recessed portion 944 is defined by radially inwardlyfacing semi-cylindrical surface 948 and a radially extending verticalsurface 950. Vertical surface 950 is adjacent crimp surface 942 and issubstantially perpendicular thereto. The corner of vertical surface 950and crimp surface 942 defines a first end or edge 952. Similarly, thevertical surface of recessed portion 946 defines a second end or edge954. Furthermore, two protrusions or extensions 954 and 956 extend fromthe sides of die 914 for lateral alignment of the crimp dies.Protrusions 954 and 956 are defined by angled surfaces 958 and 960,respectively, and horizontal surfaces 962 and 964, respectively.

It is noted that the semi-cylindrical recessed portions described forthe dies 912 and 914 is only a preferred embodiment and the recessedportions do not necessarily need to be semi-cylindrical and can be anyshape desired.

To crimp the sleeve 822, the cover 826 and the optical fiber 900 areplaced between the crimp dies 912 and 914. The simultaneous compressionof the deformable portion of the sleeve and the cover is achievedpreferably by aligning the sleeve with surface 942 of die 914, thevertical surfaces of each recessed portion 944 and 946 on die 914 andthe surface 916 on die 912. However, the sleeve can be aligned with anyof the surfaces desired to achieve the desired result. For example, thesleeve can be aligned with the vertical surfaces of die 912.

Prior to crimping, the combination of the sleeve 822, the cover 926 andthe optical fiber 900 is placed on die 914 with first external shoulder858 being positioned in recessed portion 944 and second externalshoulder 860 being positioned in recessed portion 946. The verticalsurfaces of each recessed portion are spaced relative to each other tofit with the shoulders of the sleeve 822 and properly fit the sleevetherein. In other words, the shoulders and recessed portions areproperly configured so that the majority of the sleeve and cover arealigned and properly compressed. As stated above, the internal shouldersand the external shoulders of the sleeve are configured for alignment ofthe cover within the sleeve.

Once the sleeve 822 is properly positioned on the second die 914, thefirst die 912 is moved in the direction of the sleeve. Crimp surfaces916 and 942 are generally aligned and parallel and then forcefullycompress the sleeve portion. The height of the compression is governedby the depth of the recessed surface 942. The semi-cylindrical recessedportions in the first die 912 allow the first and second shoulders ofthe sleeve to avoid any compression forces.

As the dies engage the sleeve, the alignment of the dies is maintainedby the combination of protrusions 954 and 956 and the recessions 930 and932. These protrusions and recessions interlock and maintain thealignment of both the crimp surfaces 916 and 942 and the recessedportions 918 and 944 and 920 and 946. Additionally, these protrusionsand recessions maintain lateral alignment of the upper and lower dieswhich is important to prevent shearing of the optical fiber in the crimpsleeve. Lateral misalignment of the two dies can cause unevencompression of the sleeve, resulting in potential fracture of thecrimped optical fiber.

The result of the die compressed sleeve and cover is that the coversubstantially fills an inner volume of the sleeve, which allows for anlarge frictional area between the sleeve and cover, as described above.The resulting product is similar to that of FIG. 3 and any descriptionof the benefits and structure of the embodiments discussed above isapplicable to this embodiment.

Furthermore, as shown in FIG. 27, a metal or plastic alignment ferrule966 can be placed in the second end 978 of the sleeve. Ferrule 966 issubstantially similar to ferrule 18 and the description of ferrule 18 isapplicable to ferrule 966. In the present embodiment, sleeve 822 a hasan inner cylindrical surface 968 adjacent first open end 970 defining athrough passageway 972 therethrough. Surface 968 is adjacent axiallyfacing outwardly extending surface 976 that extends to cylindricalsurface 978, which extends to tapered surface 868 a, as discussed abovefor sleeve 822. Second open end 671 is similar to end 850 of sleeve 822.

Ferrule 218 may be inserted though second end 978 and one end of ferrule966 abutting surface 976. Ferrule 966 has a through passageway 977 forthe passage of an optical fiber. Disposed within the connector bodyprior to crimping may be an fiber optic cable 238 either with thebuffered layer or optical fiber surrounded by a thermoplastic elastomertube 240, as described above.

FIG. 28 shows two sleeves having a similar configuration as sleeve 822a; however, positioned in the second ends 978 of the sleeves 822 a and822 b is a splice element 980. Splice element 980 is preferably formedfrom ceramic or glass, but can be any suitable material and issubstantially cylindrical. Through passageway 982 extends from openended first end 984 to open ended second end 986. Through passageway 982is defined by an inwardly tapered surface 988 which extends from thefirst end to cylindrical surface 990 and then to oppositely taperedsurface 992, which is adjacent second end 986. Splice element 980 allowstwo different sleeves 822 a and 822 b to be coupled together.

FIG. 29 shows a cover 826 a disposed within a sleeve 822 c that isconfigured to receive a fiber alignment member 1000. An optical fiber900 extends through the cover and sleeve as described above. Cover 826 aand sleeve 822 c are substantially similar to cover 826 and sleeve 822described above, except that end 1002 of sleeve 822 c is configured toreceive the end of alignment member 1000. More specifically, end 1002has a U-shaped recessed portion 1004 therein. Recessed portion 1004 isdefined by two axially facing surfaces 1006 and 1008 and inwardlyradially facing surface 1010.

Alignment member 1000 has a first open end 1012, a second open end 1014and a through passageway 1016 extending from the first end to the secondend. Adjacent first end, through passageway 1016 is defined by asubstantially cylindrical inner surface 1018, which extends to outwardlytapered surface 1020. Tapered surface 1020 is adjacent substantiallycylindrical inner surface 1022, which extends to the second end 1014. Apre-polished fiber stud is positioned within through passageway 1016adjacent the first end and is affixed to surface 1018 using adhesive.Optical fiber 900 preferably mates with the glass fiber cleaved end face1026 and is affixed thereto using a index-matching gel.

While specific embodiments have been chosen to illustrate the invention,it will be understood by those skilled in the art that various changesand modifications can be made therein without departing from the scopeof the invention as defined in the appended claims.

1. A crimp tool for forming a strain relief connector, the strain reliefconnector being generally cylindrical and having first and secondexternal shoulders, said tool comprising: a first crimp portion having afirst generally planar surface with first and second ends; a secondcrimp portion having a second generally planar surface with third andfourth ends; said first and second surfaces being generally aligned whencrimping, with said first and second shoulders of the strain reliefconnector abutting said first and third ends and said second and fourthends, respectively.
 2. A crimp tool according to claim 1, wherein saidfirst and second ends are adjacent first and second recessed portions;and said third and fourth ends are adjacent third and fourth recessedportions; said first and second external shoulders fitting within saidfirst and third recessed portions and said second and fourth recessedportions, respectively.
 3. A crimp tool according to claim 2, whereinsaid first and third recessed portions and second and fourth recessedportions are generally aligned when crimping.
 4. A crimp tool accordingto claim 1, wherein said first and second generally planar surfaces aregenerally parallel when crimping and compress the strain reliefconnector to form a compressed portion, wherein the width is greaterthan the height thereof.